1 /* $OpenBSD: canohost.c,v 1.59 2006/07/26 13:57:17 stevesk Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Functions for returning the canonical host name of the remote site.
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
17 #include <sys/types.h>
18 #include <sys/socket.h>
20 #include <netinet/in.h>
33 static void check_ip_options(int, char *);
36 * Return the canonical name of the host at the other end of the socket. The
37 * caller should free the returned string with xfree.
41 get_remote_hostname(int sock, int use_dns)
43 struct sockaddr_storage from;
46 struct addrinfo hints, *ai, *aitop;
47 char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
49 /* Get IP address of client. */
50 fromlen = sizeof(from);
51 memset(&from, 0, sizeof(from));
52 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
53 debug("getpeername failed: %.100s", strerror(errno));
57 if (from.ss_family == AF_INET)
58 check_ip_options(sock, ntop);
60 ipv64_normalise_mapped(&from, &fromlen);
62 if (from.ss_family == AF_INET6)
63 fromlen = sizeof(struct sockaddr_in6);
65 if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
66 NULL, 0, NI_NUMERICHOST) != 0)
67 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
72 debug3("Trying to reverse map address %.100s.", ntop);
73 /* Map the IP address to a host name. */
74 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
75 NULL, 0, NI_NAMEREQD) != 0) {
76 /* Host name not found. Use ip address. */
81 * if reverse lookup result looks like a numeric hostname,
82 * someone is trying to trick us by PTR record like following:
83 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
85 memset(&hints, 0, sizeof(hints));
86 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
87 hints.ai_flags = AI_NUMERICHOST;
88 if (getaddrinfo(name, "0", &hints, &ai) == 0) {
89 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
96 * Convert it to all lowercase (which is expected by the rest
99 for (i = 0; name[i]; i++)
100 if (isupper(name[i]))
101 name[i] = (char)tolower(name[i]);
103 * Map it back to an IP address and check that the given
104 * address actually is an address of this host. This is
105 * necessary because anyone with access to a name server can
106 * define arbitrary names for an IP address. Mapping from
107 * name to IP address can be trusted better (but can still be
108 * fooled if the intruder has access to the name server of
111 memset(&hints, 0, sizeof(hints));
112 hints.ai_family = from.ss_family;
113 hints.ai_socktype = SOCK_STREAM;
114 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
115 logit("reverse mapping checking getaddrinfo for %.700s "
116 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop);
117 return xstrdup(ntop);
119 /* Look for the address from the list of addresses. */
120 for (ai = aitop; ai; ai = ai->ai_next) {
121 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
122 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
123 (strcmp(ntop, ntop2) == 0))
127 /* If we reached the end of the list, the address was not there. */
129 /* Address not found for the host name. */
130 logit("Address %.100s maps to %.600s, but this does not "
131 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!",
133 return xstrdup(ntop);
135 return xstrdup(name);
139 * If IP options are supported, make sure there are none (log and
140 * disconnect them if any are found). Basically we are worried about
141 * source routing; it can be used to pretend you are somebody
142 * (ip-address) you are not. That itself may be "almost acceptable"
143 * under certain circumstances, but rhosts autentication is useless
144 * if source routing is accepted. Notice also that if we just dropped
145 * source routing here, the other side could use IP spoofing to do
146 * rest of the interaction and could still bypass security. So we
147 * exit here if we detect any IP options.
151 check_ip_options(int sock, char *ipaddr)
155 char text[sizeof(options) * 3 + 1];
156 socklen_t option_size;
161 if ((ip = getprotobyname("ip")) != NULL)
162 ipproto = ip->p_proto;
164 ipproto = IPPROTO_IP;
165 option_size = sizeof(options);
166 if (getsockopt(sock, ipproto, IP_OPTIONS, options,
167 &option_size) >= 0 && option_size != 0) {
169 for (i = 0; i < option_size; i++)
170 snprintf(text + i*3, sizeof(text) - i*3,
171 " %2.2x", options[i]);
172 fatal("Connection from %.100s with IP options:%.800s",
175 #endif /* IP_OPTIONS */
179 ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len)
181 struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr;
182 struct sockaddr_in *a4 = (struct sockaddr_in *)addr;
183 struct in_addr inaddr;
186 if (addr->ss_family != AF_INET6 ||
187 !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr))
190 debug3("Normalising mapped IPv4 in IPv6 address");
192 memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr));
193 port = a6->sin6_port;
195 memset(addr, 0, sizeof(*a4));
197 a4->sin_family = AF_INET;
199 memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr));
204 * Return the canonical name of the host in the other side of the current
205 * connection. The host name is cached, so it is efficient to call this
210 get_canonical_hostname(int use_dns)
213 static char *canonical_host_name = NULL;
214 static char *remote_ip = NULL;
216 /* Check if we have previously retrieved name with same option. */
217 if (use_dns && canonical_host_name != NULL)
218 return canonical_host_name;
219 if (!use_dns && remote_ip != NULL)
222 /* Get the real hostname if socket; otherwise return UNKNOWN. */
223 if (packet_connection_is_on_socket())
224 host = get_remote_hostname(packet_get_connection_in(), use_dns);
229 canonical_host_name = host;
236 * Returns the local/remote IP-address/hostname of socket as a string.
237 * The returned string must be freed.
240 get_socket_address(int sock, int remote, int flags)
242 struct sockaddr_storage addr;
244 char ntop[NI_MAXHOST];
247 /* Get IP address of client. */
248 addrlen = sizeof(addr);
249 memset(&addr, 0, sizeof(addr));
252 if (getpeername(sock, (struct sockaddr *)&addr, &addrlen)
256 if (getsockname(sock, (struct sockaddr *)&addr, &addrlen)
261 /* Work around Linux IPv6 weirdness */
262 if (addr.ss_family == AF_INET6)
263 addrlen = sizeof(struct sockaddr_in6);
265 ipv64_normalise_mapped(&addr, &addrlen);
267 /* Get the address in ascii. */
268 if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop,
269 sizeof(ntop), NULL, 0, flags)) != 0) {
270 error("get_socket_address: getnameinfo %d failed: %s", flags,
271 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
274 return xstrdup(ntop);
278 get_peer_ipaddr(int sock)
282 if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL)
284 return xstrdup("UNKNOWN");
288 get_local_ipaddr(int sock)
292 if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL)
294 return xstrdup("UNKNOWN");
298 get_local_name(int sock)
300 return get_socket_address(sock, 0, NI_NAMEREQD);
304 * Returns the IP-address of the remote host as a string. The returned
305 * string must not be freed.
309 get_remote_ipaddr(void)
311 static char *canonical_host_ip = NULL;
313 /* Check whether we have cached the ipaddr. */
314 if (canonical_host_ip == NULL) {
315 if (packet_connection_is_on_socket()) {
317 get_peer_ipaddr(packet_get_connection_in());
318 if (canonical_host_ip == NULL)
321 /* If not on socket, return UNKNOWN. */
322 canonical_host_ip = xstrdup("UNKNOWN");
325 return canonical_host_ip;
329 get_remote_name_or_ip(u_int utmp_len, int use_dns)
331 static const char *remote = "";
333 remote = get_canonical_hostname(use_dns);
334 if (utmp_len == 0 || strlen(remote) > utmp_len)
335 remote = get_remote_ipaddr();
339 /* Returns the local/remote port for the socket. */
342 get_sock_port(int sock, int local)
344 struct sockaddr_storage from;
346 char strport[NI_MAXSERV];
349 /* Get IP address of client. */
350 fromlen = sizeof(from);
351 memset(&from, 0, sizeof(from));
353 if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
354 error("getsockname failed: %.100s", strerror(errno));
358 if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) {
359 debug("getpeername failed: %.100s", strerror(errno));
364 /* Work around Linux IPv6 weirdness */
365 if (from.ss_family == AF_INET6)
366 fromlen = sizeof(struct sockaddr_in6);
368 /* Return port number. */
369 if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
370 strport, sizeof(strport), NI_NUMERICSERV)) != 0)
371 fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed: %s",
372 r == EAI_SYSTEM ? strerror(errno) : gai_strerror(r));
373 return atoi(strport);
376 /* Returns remote/local port number for the current connection. */
382 * If the connection is not a socket, return 65535. This is
383 * intentionally chosen to be an unprivileged port number.
385 if (!packet_connection_is_on_socket())
388 /* Get socket and return the port number. */
389 return get_sock_port(packet_get_connection_in(), local);
393 get_peer_port(int sock)
395 return get_sock_port(sock, 0);
399 get_remote_port(void)
401 static int port = -1;
403 /* Cache to avoid getpeername() on a dead connection */